Effects of Cationic Substitutions on Delayed Rectifier Current in Type I Vestibular Hair Cells

Effects of Cationic Substitutions on Delayed Rectifier Current in Type I Vestibular Hair Cells
Rennie, K.J. ; Correia, M.J.
2000-01-15 00:00:00
The resting potassium current (I
KI
) in gerbil dissociated type I vestibular hair cells has been characterized under various ionic conditions in whole cell voltage-clamp. When all K+ in the patch electrode solution was replaced with Na+, (Na+)
in
or Cs+, (Cs+)
in
, large inward currents were evoked in response to voltage steps between −90 and −50 mV. Activation of these currents could be described by a Hodgkin-Huxley-type kinetic scheme, the order of best fit increasing with depolarization. Above ∼−40 mV currents became outward and inactivated with a monoexponential time course. Membrane resistance was inversely correlated with external K+ concentration. With (Na+)
in
, currents were eliminated when K+ was removed from the external solution or following extracellular perfusion of 4-aminopyridine, indicating that currents flowed through I
KI
channels. Also, reduction of K+ entry through manipulation of membrane potential reduced the magnitude of the outward current. Under symmetrical Cs+, 0 K+ conditions I
KI
is highly permeable to Cs+. However, inward currents were reduced when small amounts of external K+ were added. Higher concentrations of K+ resulted in larger currents indicating an anomalous mole fraction effect in mixtures of external Cs+ and K+.
http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.pngThe Journal of Membrane BiologySpringer Journalshttp://www.deepdyve.com/lp/springer-journals/effects-of-cationic-substitutions-on-delayed-rectifier-current-in-type-oOQWbDmAcG

Effects of Cationic Substitutions on Delayed Rectifier Current in Type I Vestibular Hair Cells